Table of Content

28 September 2026, Volume 36 Issue 9

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Safety Technology and Engineering Public Safety and Emergency Management Occupational Health Intelligent Safety Technology

Safety Technology and Engineering

Review on explosion hazard characteristics of syngas and its inerting suppression technology

Luo Zhenmin, Hao Ruolin, Su Bin, Liu Litao, Liu Lu, Wang Tao

2026, 36(9):  1-8.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0319

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A systematic analysis is conducted on the ignition sensitivity, explosion kinetics, and oxidation mechanisms of syngas, as well as advances in inerting and explosion suppression technologies, based on two decades of global research findings.The variations in key ignition parameters (explosion limits, minimum ignition energy (MIE), and ignition delay time (IDT)) are explored to clarify the impacts of hydrogen fraction, temperature, pressure, and turbulence on syngas ignition performance. Corresponding explosion behaviors, including explosion pressure, pressure rise rate, laminar burning velocity, and flame propagation, are investigated to reveal the effects of component ratio, boundary conditions, and spatial structure on explosion kinetics. The dominant H₂/CO oxidation pathways and critical free radical reactions are summarized to clarify the correlation between microscopic mechanisms and macroscopic explosion characteristics under multi-factor coupling. N₂/CO₂ inerting, water mist, chemical suppressants, and composite suppression technologies are also reviewed, and their technical characteristics and applicable conditions are compared. The results show that higher hydrogen content enhances syngas reactivity and explosion risks. CO₂ presents better inerting performance than N₂, and composite suppression systems realize optimal explosion mitigation through multi-mechanism synergy.Existing studies have limitations in multi-factor coupling mechanism cognition, unified evaluation criteria, model universality, and engineering-scale validation. Future research should focus on multi-field coupling analysis under complex conditions, establish standardized evaluation systems, and promote the intelligent and engineering application of syngas explosion prevention technologies.

Experimental study on combustion and fire spread characteristics of liquid-fuel-soaked loess beds with different particle gradations

Chen Changkun, Wang Qijiang, Liu Shishan, Shi Lang

2026, 36(9):  9-16.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0244

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To effectively prevent and control soil environmental fires caused by liquid fuel leaks, and to advance post-disaster environmental decontamination efforts, and to investigate the influence of particle gradation on flame spread behavior in liquid-fuel-soaked porous media, combustion experiments were conducted on 0# diesel-soaked loess beds with different particle gradations. Structural parameters, internal temperature distributions, burning rates, and flame spread rates were measured and analyzed to explore the influence mechanism of particle gradation on the combustion process of the soaked bed. It was found that particle gradation significantly affects flame spread behavior by altering the porosity, dry bulk density, particle contact conditions, and pore connectivity of the loess bed. With increasing particle diameter, the pore scale increases and the dominant heat transfer mechanism gradually shifts from solid-phase conduction to convective heat transfer, leading to enhanced heat transfer and higher internal temperatures. The average burning rate is closely related to the pore structure of the loess bed. The combustion rate of the matrix particle size d_b=0.116 mm series operating conditions shows an overall decreasing trend with the increase of particle size d_a added. Whereas for the d_b=1.800 mm and d_b=4.375 mm series, it first increased and then decreased due to the combined effects of heat transfer enhancement and fuel transport variation. In addition, the flame spread rate first decreases and then increases with increasing particle diameter, exhibiting a critical particle size. A fire spread rate prediction model based on effective particle diameter was established and shows good performance under small particle-size conditions.

Study on suppression effects of H₂/TiH₂ mixed explosion with composite modified dry water

Pei Bei, Lyu Hang, Zhou Lei, Lu Chang, Ji Wentao, Kan Qiang

2026, 36(9):  17-25.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0592

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Metal hydride-based solid-state hydrogen storage has the advantage of high energy density. However, metal hydride dust/H₂ gas-powder two-phase mixtures are easily formed during production. This leads to an extremely high explosion risk. To efficiently suppress suppression of metal hydride dust/H₂ gas-powder two-phase mixture, a novel C₆F₁₂O and K₂CO₃ composite modified dry water, denoted as PC-PMDW, This material was developed based on inert dilution, physical cooling, and chemical chain inhibition. A closed explosion pipeline system was used. The explosion-suppression performance of PC-PMDW at mass fractions of 40%-100% was compared with that of single K₂CO₃-modified dry water (PC-DW). The results show that the explosion-suppression performance of PC-PMDW is significantly better than that of PC-DW. At a mass fraction of 100%, the explosion pressure is reduced by 70.27%. The average flame propagation velocity is reduced by 91.08%, and the flame can no longer propagate to the end of the pipeline. Based on test of the microstructure and composition of the explosion products, the suppression effect is mainly attributed to synergistic effects. These effects include heat absorption evaporation of C₆F₁₂O and water, dilution of combustible gases by CO₂ released from K₂CO₃,thermal decomposition, capture of key radicals such as H, O, and OH by active potassium compounds and fluorine-containing radicals, and oxygen isolation through surface coating, thereby weakening thermal feedback and interrupting the explosion chain reaction.

Effect of EMC vapor on explosion characteristics of thermal runaway products of lithium-ion batteries

Zhang Ying, Peng Zicong, Li Qi, Zhang Churan, Han Jinghao, Chen Yue

2026, 36(9):  26-34.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0044

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To clarify the mixed explosion characteristics of high-temperature electrolyte vapor and thermal runaway gases from lithium-ion batteries, and to reveal the effect of such vapor on the explosion hazard of battery thermal runaway products, we conducted systematic tests in a 20 L spherical apparatus on gas mixtures of different state of charge (SOC) batteries and EMC vapor, combined with computational fluid dynamics (CFD) simulation and chemical kinetics analysis to deeply examine the explosion evolution behavior. The findings reveal that high temperature exerts both a physical dilution effect and a chemical kinetic enhancement effect. Thermodynamically, the high-calorific EMC vapor combined with 100% SOC gas results in significant energy superposition, leading to the highest maximum explosion pressure. Kinetically, oxygen-containing radicals generated by the thermal decomposition of EMC at high temperatures accelerate the core chain-branching reactions, causing the maximum rate of pressure rise for low-SOC gases to increase by over 240%. Moreover, the acceleration of microscopic reactions further induces macroscopic flow instability, forming a physico-chemical coupling mechanism.

Study on thermal runaway characteristics of large-capacity ternary lithium-ion batteries under upright and inverted placement orientations

Fan Chuan'gang, Shang Jialiang, Pan Zhenfei, Shi Cunxiang, Luo Tuantuan, Huang Peifeng

2026, 36(9):  35-43.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0239

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To investigate the effect of placement orientation on thermal runaway behavior of large-format NCM batteries, overheating-induced thermal runaway tests were conducted on 135 Ah prismatic NCM batteries under upright and inverted orientations. First, thermal runaway onset, temperature and voltage responses, and internal propagation behavior were compared. Jet temperature, mass loss, heat release, and smoke generation were then analyzed. Finally, eight characteristic parameters were selected from three aspects: thermal runaway onset, propagation, and jet hazards. A radar chart-based model was developed to assess runaway hazards. The results show that, compared with the upright orientation, the inverted orientation delayed runaway onset from 1 032.5 s to 1 093.0 s. However, after runaway occurred, the maximum surface temperature, maximum temperature rise rate, and propagation rate increased by 14.3%, 27.7%, and 27.6%, respectively. The maximum jet temperature also increased by 110.1 ℃. No significant differences were observed in total heat release or total smoke production between the two orientations. Although the inverted orientation increases runaway onset threshold, it significantly intensifies the hazards after runaway. Therefore, the overall runaway hazard is greater under the inverted orientation than under the upright orientation.

Reaction kinetic modeling of ammonium nitrate thermal decomposition

Ji Wentao, Lu Yuqin, Guo Jiajun, Wang Yan, Zhang Jingyue, Xu Yabei

2026, 36(9):  44-51.  doi:10.16265/j.cnki.issn1003-3033.2026.09.1424

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To deeply reveal the thermal decomposition mechanism of NH₄NO₃, two kinetic models applicable to the thermal decomposition reaction of NH₄NO₃, namely the 3-1 model (three species and one reaction) and the 4-4 model (four species and four reactions), are constructed based on thermogravimetric (TG) experimental data and CRNN algorithm. The model can predict the TG curves and the material evolution during the thermal decomposition process of NH₄NO₃, and infer the reaction pathway and intermediate products. The results show that in the 3-1 model, the calculated activation energy is 98.49 kJ/mol, which is in good agreement with the experimental value. Based on the reaction network constructed using the 4-4 model, two initial reaction paths are identified, with corresponding activation energies of 98.02 kJ/mol and 139.43 kJ/mol, respectively. The entire thermal decomposition process involves the breaking of ionic bonds between NH₄⁺ and NO₃^-, hydrogen transfer reactions, autocatalytic reactions, and interactions between products. NO_2, as a key intermediate product, participates in multiple subsequent reaction paths, ultimately generating substances such as NO₂, N₂O, NO, N₂, O₂, and H₂O.

Experimental investigation of explosion suppression in H₂/NH₃/air mixtures using Na₂CO₃-5A zeolite composite powder

Zheng Kai, Zhou Chen, Sun Yuwei, Wu Haonan, Zhao Yuyang, Shen Shuaihang

2026, 36(9):  52-60.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0314

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To suppress H₂/NH₃/air explosions, Na₂CO₃-5A zeolite composite powder was prepared and its explosion suppression performance was investigated. The composite powder is characterized using scanning electron microscopy (SEM), laser particle size analysis, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Its performance is evaluated through explosion suppression tests, focusing on flame evolution shape, flame length, and overpressure in stoichiometric hydrogen-rich H₂/NH₃/air explosions. The effects of varying hydrogen fractions in fuel (50%, 60%, and 70%), the mass ratio of Na₂CO₃ in the composite powder, and the concentration of the composite powder are examined. The results demonstrate that the prepared composite powder exhibits excellent structural and thermal properties. The composite powders exhibit superior explosion suppression capabilities for H₂/NH₃/air mixtures, as evidenced by a reduction in flame propagation speed and overpressure, as well as an extension of explosion flame duration and the time to reach maximum overpressure. For all H₂/NH₃/air mixtures, as the mass ratio of Na₂CO₃ and the concentrations of composite powder change, the explosion suppression performance of the powder first increases and then decreases, with the optimal values corresponding to 60% and 100 g/m³. The research findings can provide theoretical support and technical assistance for the explosion prevention and control of hydrogen-ammonia mixed fuels.

Study on pyrolysis characteristics and fire hazard of surface combustible materials from ancient cypress

Zhao Jingyu, Ming Hanqi, Song Jiajia, Shuai Xingyu, Zhang Yanni, Deng Jun

2026, 36(9):  61-70.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0279

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To support fire risk assessment and fire prevention management in ancient cypress forests, the bark, leaves, and branches of ancient cypress were selected as the research objects. Proximate analysis and thermal analysis tests in air were conducted to investigate the compositional characteristics, mass-loss processes, heat-release behaviors, and effects of heating rate on the pyrolysis of different combustible materials. Iso-conversional methods were employed to analyze the kinetic characteristics in the main pyrolysis reaction region. The average apparent activation energy, total heat release, and peak heat flux were selected as evaluation indicators, and the entropy weight method was used to determine the fire hazard of different combustible materials. The results show that the bark, leaves, and branches all exhibit three characteristic stages of dehydration, rapid mass loss, and burnout. The main mass-loss region is 200-500 ℃, and the major exothermic peaks are concentrated at 300-460 ℃. Heat release is mainly attributed to the oxidation of volatile products and residual char in air. The bark has an ash content of 21.78% and a pyrolysis residue yield of 18%-24%, indicating that its pyrolysis progression is hindered. The leaves have the lowest average apparent activation energy (164.03 kJ/mol), indicating that pyrolysis occurs more readily. The branches exhibit a total heat release of 5 796.33 J/g and show a stronger capacity for sustained heat supply. The fire hazard is ranked as branches > leaves > bark.

Analysis of hydrogen leakage and diffusion and hazardous zone division in confined space based on COMSOL

Mu Shifang, Wang Zhonglan, Shang Rujing, Ji Wentao, Wang Yan

2026, 36(9):  71-77.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0879

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To enhance risk prevention in hydrogen energy application scenarios, the COMSOL Multiphysics software was used to simulate hydrogen leakage and diffusion in confined spaces. A two-dimensional geometric model was constructed to systematically study hydrogen mass concentration distribution characteristics under varying leakage aperture sizes, wind speeds, obstacle heights, and distances between obstacles and leakage apertures. Mass concentration distribution maps and contour plots were generated to reveal hydrogen leakage and diffusion patterns. Based on hydrogen explosion limit, flammable and explosive hazardous zones were delineated, and the temporal evolution of hazardous ranges was quantified. The findings indicate that larger leakage apertures result in more extensive hydrogen cloud volumes, with the horizontal diffusion distance increasing by approximately 2 m at t=15 s for a 40 mm aperture compared to a 20 mm one, significantly elevating hazard levels. Obstacles alter diffusion pathways and inhibit vertical propagation, reducing the vertical diffusion distances by 1.5 m for obstacles of 4 m height relative to unobstructed conditions, though excessively tall obstacles may cause localized high-concentration accumulations.

Fire detection algorithm based on multi-scale feature fusion and dynamic attention

Li Dong, Huo Yinuo, Yang Xianzhi, Wang Rui, Liu Yuzhi, Wang Jingwu

2026, 36(9):  78-84.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0630

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To reduce the missed detection rate of fire detection in complex scenes and improve the anti-interference ability for flame and smoke targets, a fire detection algorithm based on a deep learning object detection framework was proposed. First, YOLOv8n was used as the baseline network, and a wavelet transform convolution (WTConv) module was introduced in the downsampling stage of the feature pyramid to retain high-frequency details of flame edges and smoke textures. Second, a poly-kernel lightweight Inception block (PKLBlock) was constructed in the feature fusion stage, and multi-scale feature fusion was performed through multi-branch convolution and contextual anchor attention. Third, a non-local attention (NLAttention) module was incorporated into the detection feature layer, and a dynamic attention mechanism was used to establish long-range dependencies between fire and smoke targets and surrounding regions. Finally, ablation and comparative performance evaluation were conducted using a self-built fire and smoke image dataset to evaluate the algorithm's performance. The results show that the algorithm achieves a precision of 93.46%, a recall of 88.48%, an F₁ score of 90.90%, and a mean average precision (mAP) of 92.04% at an intersection over union threshold of 0.5 (mAP@0.5). Compared with YOLOv8n, they are increased by 5.24, 2.13, 3.62 and 3.87 percentage points, respectively. The inference speed is 31.2 frames/s. The algorithm can detect flame and smoke targets in real time and provides algorithmic support for early fire warning in video monitoring scenarios.

Gas discharge impulse model in local application fire systems

Ma Jianqin, Yang Fan, Wang Haoxuan, Zhao Qingsong

2026, 36(9):  85-93.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0240

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To address the safety technical issue in local application fire suppression systems for Class B pool fires, where the gas discharge impulse plays a dual role of both highly effective flame knockdown and inducing splashing, a systematic gas discharge impulse prediction model was developed and experimental studies were conducted. Firstly, an array-based dynamic pressure measurement device was designed and fabricated to accurately quantify the spatial distribution and transient evolution of the gas discharge impulse field beneath the nozzle. Based on experimental data, a predictive model was established, incorporating both discharge pressure and duration. Secondly, a comprehensive fire suppression effectiveness model was constructed, which comprised two sequential phases: flame knockdown and extinguishment. A flame lift force calculation model based on plume theory was established, and the critical extinguishment criterion was defined as the gas discharge impulse exceeding the flame lift force. Finally, a surface tension criterion for central splash and a geometric morphology criterion for edge overflow were proposed innovatively to quantify the upper impulse threshold for safe discharge. The results demonstrate that the developed models and device can accurately predict both the critical impulse required for successful extinguishment and the upper safety limit for splashing. The extinguishment was observed to occur during the peak impulse release and early decay stages, which is consistent with the theoretical criterion prediction. The predicted splash behavior also agrees well the experimental observations, thereby validating the effectiveness of the dual-criterion approach.

Effects of directional venting duct structure on flame propagation and overpressure evolution of hydrogen-blended natural gas

Yang Xufeng, Jiang Baoping, Yang Wen, Zhang Kun, Zhang Yuchun

2026, 36(9):  94-102.  doi:10.16265/j.cnki.issn1003-3033.2026.09.2107

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To mitigate explosion hazards in hydrogen-blended natural gas pipelines and enhance the safety level of gas transmission infrastructure, this study independently designed and constructed a pipeline explosion experimental platform. A systematic comparison was conducted on the explosion characteristics of hydrogen-blended natural gas (i.e., CH₄/H₂/air mixtures) under three configurations: without a venting duct, with a horizontal venting duct, and with a 60° bifurcated venting duct. The study focused on analyzing the influence different directional venting duct structures on flame propagation dynamics and overpressure development inside the pipeline. The results demonstrate that, compared to the open-space condition without a venting duct, the confined directional venting configuration intensifies secondary explosions within the duct, leading to a significant increase in both explosion overpressure and flame propagation speed. In contrast to horizontal directional venting, the bifurcated structure at the entrance of the bifurcated directional venting duct reduces the flow velocity of the vented gas, prolonging the time required for the flame front to propagate into the venting duct and delaying the peak values of both flame speed and explosion overpressure. Compared to the horizontal directional venting duct, the bifurcated design reduces the maximum flame propagation speed, peak explosion overpressure, and maximum rate of pressure rise by 9%, 30%, and 24%, respectively.

Methodology for explosion-proof resilience assessment of continuous stirred tank reactors driven by process parameters

Sun Hao, Huang Jin, Shi Jihao, Wang Fuyu, Qi Meng

2026, 36(9):  103-110.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0029

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To effectively prevent explosion accidents in continuous reactors due to thermal runaway during operation, this study proposed a reactor explosion accident prevention method that integrates dynamic simulation and resilience assessment. Firstly, based on the operating characteristics of the reactor and the mechanism of thermal runaway, key process parameters such as temperature and pressure were identified, and potential interference events are systematically recognized. Secondly, dynamic simulation was carried out using ASPEN HYSYS to analyze the time-varying characteristics of key process parameters under different interference events. On this basis, considering the multi-dimensional nature and time-varying characteristics of process parameters, a process parameter-driven resilience assessment model for the reactor system was constructed using the optimal-worst algorithm (BWM), and the overall resilience of the reactor system was evaluated. Finally, targeted resilience improvement strategies were proposed based on the assessment results, thereby preventing explosion accidents in continuous reactors. Taking the continuous reactor as an example, typical interference scenarios were simulated and resilience assessment was conducted to verify the accuracy and applicability of the method. The research results show that by coupling dynamic simulation with resilience assessment, the impact mechanism of interference events on the safety status of the reactor can be systematically revealed. By improving the system resilience, the key process parameters of the reactor can be controlled within the safety threshold, providing a theoretical basis and practical path for the transformation from passive response to active prevention in accident prevention.

Study on overcharge thermal runaway characteristics of LiFePO₄ batteries under different constraint effects

Yang Fan, Bai Panxing, Ping Xiaofan, Zhang Cunfu, Cao Xi, Yang Yuxuan

2026, 36(9):  111-119.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0508

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To mitigate thermal runaway fire and explosion accidents induced by overcharge of lithium-ion batteries and to improve the understanding of the coupling regulation mechanism of fixture constraint, confined space and ignition conditions, this study systematically investigated the evolution of thermal runaway, temperature response, and voltage variation of a 314 Ah prismatic LiFePO₄ battery under 0.5C overcharge by adjusting these three factors. The results show that under unconstrained conditions, unconstrained battery swelling leads to safety valve failure and directly triggers an explosion; before the explosion, the peak surface temperatures are 50.78 ℃ in open space and 54.06 ℃ in confined space. Under constrained conditions, the safety valve opens normally and energy is released in the form of smoke or jet fire; the peak back temperature reaches 458.93 ℃ in open space with ignition, which is significantly higher than 291.13 ℃ in confined space with ignition. In confined space, unignited smoke, being denser, accumulated at the bottom, and a violent jet fire reaching a height of 1.5 m with a peak flame temperature of 701.87 ℃ is formed upon ignition. The voltage evolution is presented as a “rise-plateau-steep rise-drop” pattern, whereas the complete drop process is absentunder unconstrained conditions due to structural damage.

Study on physical and chemical properties, pyrolysis behaviors and combustion characteristics of fireproof sealant

Zhang Liang, Ou Weilei, Zhang Jincheng, Zhou Xi, Liu Wei, Ding Yanming

2026, 36(9):  120-127.  doi:10.16265/j.cnki.issn1003-3033.2026.09.1312

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To enhance the fire resistance performance of fire stopping materials, this study selected fire-resistant sealant as the research object. Conventional physical and chemical property tests were conducted, and thermogravimetry-Fourier transform infrared (TG-FTIR) coupled experiments as well as cone calorimeter tests were performed to reveal its pyrolysis and combustion characteristics from the microscale to the laboratory scale. This paper aimed to investigate the pyrolysis behaviors of fireproof sealant in nitrogen and air atmospheres and its combustion characteristics under different radiation heat fluxes. The results show that the micro-scale pyrolysis process in nitrogen could be divided into three stages corresponding to ammonium polyphosphate, melamine and acrylic acid, while the presence of oxygen promotes the merging of the reaction stages of ammonium polyphosphate and melamine during the micro-scale combustion process in air. Before 850 K, ammonia is the main gaseous product in nitrogen, while substantial amounts of ammonia, CO₂ and H₂O are released in air. After 850 K, CO₂ and H₂O are produced in both nitrogen and air atmosphere. With the increase of external heat radiation flux in bench-scale cone experiment, the ignition time is shortened, and the generation rate and peak value of harmful gas emissions increase. The calculated fire evaluation indexes indicate the increased fire risk of the material. The current study can be helpful for deeply revealing the fire prevention mechanism of fireproof sealant and providing a reference for engineering applications.

Effect of environmentally friendly nanoparticles on foam stability and suppression property

Zhang Yixiang, Cao Shiqi, Feng Shilong, Jiang Huayi

2026, 36(9):  128-135.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0045

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To improve the emergency handling ability of high expansion foam to mitigate the leakage and diffusion of cryogenic liquids such as liquefied natural gas (LNG) and pool fire combustion, three environmental-friendly nanoparticles with natural sources, degradability and stable structure were selected. The effects of different particle mass fractions on foaming ability and stability were experimentally tested, and the suppression effect of nanoparticles on cryogenic liquid evaporation was also analyzed. The results show that the foaming ability gradually decreases with the increasing particle concentrations, and the liquid drainage rate first increases and then decreases. The foam half-life reaches the maximum value at the lignin particle mass fraction of 0.1% and then decreases with the increasing mass fraction, while the foam stability increases with the increasing of nanofiber and nanowhisker concentrations. The foam size with the addition of lignin increases rapidly, while under the addition of nanofibers and whiskers, the increase of the foam size is relatively small as the time goes on. There are three stages of rapid evaporation, stage evaporation and decay evaporation during the foam suppression process, and the maintenance time of cryogenic liquids was extended with the presence of nanoparticles, which is beneficial for suppressing the liquid evaporation process.

Influence of environmental wind on LPG leakage dispersion from spherical tanks with a safety wall

Huang Yuanjie, Lin Dong, Han Linxu, Zhang Dina, Yang Guoliang, Zhai Xu

2026, 36(9):  136-146.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0331

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To investigate wind effects on the leakage dispersion of LPG in a spherical tank farm with a safety wall, a three-dimensional model was developed using the FLACS. Based on typical leakage scenarios in an actual spherical tank farm, different wind directions and wind speeds were considered, and the dispersion and accumulation processes of LPG vapor clouds inside and outside the safety wall were simulated. The evolution characteristics of hazardous areas were analyzed based on maximum dispersion distance, LPG volume fraction distribution in typical regions, and temporal variation of the equivalent flammable vapor cloud volume. The results show that the LPG dispersion process is initially dominated by the momentum of the leakage jet and gradually transitions to being controlled by the environmental wind field. The coupling effects of the safety wall and environmental wind significantly influence the dispersion pathway, LPG volume fraction distribution, and hazardous area evolution of the vapor cloud. Under upwind conditions, the axial transport capacity of the vapor cloud is weakened by the environmental wind, and gas cloud recirculation and accumulation are induced near the inner side of the safety wall. Consequently, a higher explosion hazard potential is observed compared with that under downwind and crosswind conditions. Under upwind conditions, the most significant accumulation occurs at a low wind speed of approximately 2 m/s, where the equivalent flammable vapor cloud volume reaches the maximum value among all simulated cases. With increasing wind speed, enhanced turbulent mixing and dilution effects promote vapor cloud dispersion, resulting in an overall reduction in the dispersion range and equivalent flammable vapor cloud volume. The results provide a theoretical basis for identifying unfavorable wind conditions and optimizing safety protection measures in LPG spherical tank areas.

Study on suspension performance of on-site preparation of fire prevention and extinguishing thickened slurry

Shao Shuzhen, Shi Shiliang, Wang Lei, Lu Yi, Xing Shunbo, Tian Shuai

2026, 36(9):  147-156.  doi:10.16265/j.cnki.issn1003-3033.2026.09.1421

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To address the engineering problems of traditional loess fire-extinguishing slurry, such as easy sedimentation, pipeline blockage and accumulation failure, and improve the suspension stability of thickened slurry, mechanical analysis of loess particles was carried out to derive the settling velocity formula. It was clarified that stirring time, stirring speed and particle size affect suspension characteristics by changing the interaction forces between particles. Combined with range analysis, variance analysis, regression analysis and response surface analysis, the priority of influencing factors and the optimal parameter range were determined, and the practicability of the parameters was verified through on-site grouting monitoring. The results show that the stirring time of slurry A and the stirring speed of slurry B can cause shear thinning of the thickened slurry, thereby changing its three-dimensional network structure and intermolecular entanglement; the size of loess particles C will affect their specific surface area, mechanical effects, and agglomeration behavior in the slurry. These three factors together affect the consistency and suspension performance of the slurry. The static suspension rate of the thickened slurry reaches the optimal level of 82.5% when A is 5 min, B is 1000 r/min, and C is 140 mesh. The primary and secondary ranking of each factor on the static suspension rate δ is B>A>C, indicating that stirring speed is a key factor affecting the static suspension rate of thickened slurry. The optimal ranges of factors influencing the suspension effect of thickened slurry materials are determined as 4.3 min ≤ A ≤ 5.9 min, B = 1000 r/min and 108 mesh ≤ C ≤ 167 mesh. The analysis results are basically consistent with those of range and variance analysis, which verifies the validity of the range and variance analysis results. Field grouting test results verify that the optimal preparation parameters obtained from laboratory experiments provide reliable guidance for on-site grouting performance.

Effects of scale and oil/water layer thickness on boilover behavior in crude oil storage tanks

Li Yueyang, Li Mingze, Jing Qi, Li Yuntao, Luan Guohua, Li Xin

2026, 36(9):  157-166.  doi:10.16265/j.cnki.issn1003-3033.2026.09.1122

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To reveal the effects of scale and oil/water layer thickness on the boilover behavior of crude oil storage tanks, this study designed and constructed an experimental platform with crude oil storage tanks of 4 different scales to systematically conduct boilover experiments under different scales and oil/water layer thicknesses. The analysis focused on boilover onset time and behavioral characteristics, oil temperature distribution and hot wave propagation rate, heat flux, and mass-related parameters. A relationship between the hot wave propagation rate and the mass burning rate was established, and the applicability of existing boilover onset time prediction models was evaluated. The results show that as tank size increases, boilover onset time grows linearly, while hot wave propagation rate increases nonlinearly, reaching 85.4% of the full-scale propagation rate at 66.7% scale, and the boilover safety distance also increases significantly with tank scale. Regarding boilover behavior, small-scale experiments mainly displayed continuous jetting, whereas large-scale experiments exhibited tumbling overflow and spreading combustion. In large-scale experiments, the effect of oil/water layer thickness on oil temperature at the same elevation was insignificant. However, with increasing oil layer thickness and decreasing water layer thickness, boilover onset time is prolonged, the proportion of overflowed fuel relative to the remaining fuel increases, and boilover intensity increases, with oil layer thickness exerting a more pronounced influence than water layer thickness.

A simplified model of combustion reaction and simulation based on multi-component small-molecule hydrocarbon

Chen Jian, Qian Wenjing, Shen Shuyi, Chen Sining, Zhou Xia, Guo Song

2026, 36(9):  167-177.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0335

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To rapidly and accurately assess the consequences of flammable and explosive chemical fire accidents. The Pyrolyzer-Gas Chromatography-Mass Spectrometry (Py-GCMS) combined device was utilized, and the combustion reaction process of flammable and explosive chemicals was reproduced through rapid heating pyrolysis experiments. The small molecule intermediate products and their proportion coefficients were obtained, and a simplified model was constructed. Further coupling was achieved with Fluent, and the calculation of the combustion and explosion process of petroleum-based liquid hydrocarbon fuels such as n-heptane was realized. The research results show that the pyrdysis products of n-heptane are significantly affected by the pyrdysis duration and the heating rate, but less by the pyrdysis temperature. Among them, the critical point for the stable combustion of n-heptane is 600 ℃. When the temperature is above this point, the content of the pyrdysis product components will remain constant. At a heating rate of 1 000 K/s and a pyrdysis duration of 8 s, the pyrdysis is the most complete. The main products are C₃, C₄, and C₅ alkanes and alkenes, which are the core components for constructing its alternative model. Compared with the Primary Reference Fuel (PRF) combustion reaction mechanism, it was found that the similarity of flame shape and characteristic gas distributions such as CO/CO₂ in the alkene substitution model was the highest. The flame geometric parameters such as flame height and flame width of the mixed substitution model had the best matching degree. However, the alkane substitution model showed significant deviations in flame distribution and the transport and diffusion of characteristic gases.

Study on flame spreading behavior and quasi-steady burning characteristics of opposed n-butanol spilling fire

Li Ranran, Yue Zhiqiang, Du Daoquan, Wang Xue, Li Manhou

2026, 36(9):  178-184.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0346

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To investigate the flame spread behavior and combustion characteristics of opposed n-butanol spilling fires under various leakage conditions, experiments was conducted using a 100 cm × 20 cm × 8 cm stainless steel channel platform, with leakage rates (9-650 mL/min) precisely controlled by a peristaltic pump. A high-frame-rate camera was employed to record the flame spread dynamics, while mass loss rates and temperature field evolution were synchronously collected using a balance, thermocouples, and a data acquisition system. The results show that as the leakage rate increases from 40 to 120 mL/min, fuel layer thickening reduces heat losses via substrate conduction and radiation transmission, leading to heat accumulation that accelerates the flame spread rate. As the leakage rate further increases to 560 mL/min, the high-speed fuel flow induces a strong forced convective cooling effect that offsets the thermal insulation effect of the fuel layer, resulting in a significant decrease in the spread rate. The burning rate per unit area exhibits four-stage evolution characteristics under low (60 mL/min), medium (120-160 mL/min), and high (290-650 mL/min) leakage rates. A calculation formula for the mass loss rate per unit area in the steady-state combustion phase, constructed based on energy conservation, yields calculation values within a relative error of ±28% compared with experimental data. With further increases in the leakage rate, the proportion of forced convective heat loss in the total energy balance increases from 28% to 57%.

Full-scale experiment on burning behaviors and smoke characteristics of spill fires in road tunnels

Ma Hanchao, Zhai Xu, Zhang Yichen, Lyu Junke, Xiao Jianfeng, Huang Hong

2026, 36(9):  185-192.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0328

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To reveal the disaster mechanism of spill fires in road tunnels and to address the shortage of full-scale experimental data, spill fire experiments were conducted in a full-scale road tunnel (100 m long, 10.5 m wide, 7.5 m high) using two fuel types (n-heptane and ethanol) and varying discharge rates (34-59 mL/s). The evolution characteristics of burning diameter, flame height, burning rate, ceiling smoke temperature, and smoke spread velocity was analyzed. The results show that the burning diameter exhibits a typical three-stage development process: "spread-shrink-quasi-steady burning". A linear relationship is found between flame height and burning diameter. During the quasi-steady stage, the burning rate of n-heptane spill fires is higher than that of ethanol, ranging from 0.055 to 0.063 mm/s and 0.039 to 0.050 mm/s, respectively. The variation trend of ceiling smoke temperature is consistent with that of the burning diameter. The smoke spread velocity under all test conditions ranges from 0.4 to 0.71 m/s and is positively correlated with the discharge rate. During the quasi-steady stage, the maximum ceiling temperature rise exhibits a linear correlation with the heat release rate. The dimensionless temperature rise decays exponentially with increasing dimensionless distance, with a decay rate slower than that predicted by existing models.

Fire suppression efficacy of dry powder-foam synergistic application under UAV payload constraints

Li Zhihan, Zhang Guowei, Li Bin, Yu Longfei, Liu Xiangfei

2026, 36(9):  193-201.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0880

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To prevent backdraft and flashover after UAV-breakable window breakage in high-rise fires, a "dry powder-foam" suppression strategy was proposed. Full-scale fire tests under UAV payload constraints were conducted by varying powder mass (1.5-4 kg) and foam flow rate (0.5-2 L/s), measuring ceiling temperature and flame height. Results show that all combinations effectively suppressed backdraft transition, exhibiting a "powder rapid suppression-foam sustained cooling" mechanism. Increasing powder mass enhanced fire suppression, with diminishing returns beyond 3 kg (only 5.6% improvement). Low foam flow (<1.5 L/s) significantly reduced cooling and increased re-ignition risk. The optimal combination (3 kg powder + 2 L/s foam) achieved the highest suppression (0.074 m/s) and cooling (3.14 ℃/s) rates.

Study on combustion characteristics of n-heptane under weak gravity

Zhang Maolin, Huang Xin, Zhao Mengke

2026, 36(9):  202-209.  doi:10.16265/j.cnki.issn1003-3033.2026.09.1543

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To investigate the effects of weak gravitational motion conditions on pool fire combustion during aircraft takeoff and landing, an inclined test platform with inclination angles ranging from 15° to 45° was first built to simulate the composite weak gravity conditions of aircraft takeoff and landing. Square fuel pools of different sizes were adopted, and sensors and high-speed cameras were used to collect data including acceleration, flame morphology and fuel burning duration. Next, the flame evolution during the sliding process was observed, and three stages were identified: initial stable stage, rapid tilting stage and oscillatory stabilization stage. The influences of inclined angle and pool size on fuel burning rate, flame tilt angle and flame height were analyzed, and the internal mechanism of flame deflection and height reduction under the combined effect of gravity and horizontal inertial force was clarified. Finally, equivalent simplification was carried out based on the laminar stagnation layer theory, and quantitative correlation models between burning rate, flame tilt angle, flame height and gravity as well as horizontal acceleration were established, respectively. The results show that the burning rate of n-heptane under sliding conditions is higher than that under static conditions. The mass loss rate of n-heptane increases first and then decreases with the rise of sliding angle, reaching its peak at 25-35°. As the pool size increases, the sensitivity of n-heptane flame tilt angle to variations in gravity and horizontal acceleration rises, while the sensitivity of flame height to such variations declines.

Validation and performance evaluation of C-SAT hydrogen jet flame length prediction model

Zhu Kunlong, Hu Hui, Wang Zhi, Zhang Bin

2026, 36(9):  210-216.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0320

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Conventional flame models are limited in addressing the buoyancy effects and low-density characteristics of hydrogen jet flames, which often lead to deviations in flame length prediction. In this study, the hydrogen jet flame length prediction model embedded in C-SAT is adopted to conduct model validation and performance evaluation. Based on multiple sets of publicly available experimental data for hydrogen jet flames, the prediction accuracies of the five virtual nozzle models (Y/O, Birch, Birch2, E/M, and Molkov) built into C-SAT are compared and screened, and the optimal model is further compared with the American Petroleum Institute(API) recommended model and the cone model in the Process Hazard Analysis Software Tool (PHAST). The results show that the Y/O model exhibits the best overall performance among the four nozzle models, with a safety factor of 1.077, a factor-of-two accuracy of 100%, a mean relative bias of -0.068, and a geometric mean bias of 0.934. In comparison with PHAST, C-SAT achieves a geometric mean bias of 0.934 and a mean relative bias of -0.068, both outperforming the API model (0.744, -0.292) and the cone model (1.132, 0.122).

Effects of flame arrester aperture ratio on propagation characteristics of premixed gasoline vapor-air flames

Mao Xiangzheng, Xu Guan'gan, Song Peng, Hu Yufeng, Xing Huadao, Xie Lifeng

2026, 36(9):  217-224.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0257

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To investigate the effects of flame arrester aperture ratio on the propagation characteristics of premixed gasoline vapor-air flames, visualization experiments on flame arresting were conducted. A high-speed camera and data recorders were employed to capture the flame propagation process and variations in parameters. The effects of the aperture ratio α (0~0.060) of flame arresters on flame morphology, flame propagation speed, overpressure, and temperature were subsequently analyzed. The results indicate that the aperture ratio significantly affects the explosion overpressure and temperature distribution. When α ≤ 0.027, the flame arrester completely suppresses flame propagation. However, a long-duration reverse oscillating flame pulsation is induced. The reverse flame amplitude decreases with increasing aperture ratio. When α ≥ 0.033, the flame arrester enhances turbulence and accelerates flame propagation. The downstream velocity peak increases with increasing aperture ratio. Under successful flame arrest, only a single overpressure peak appears, which is reduced by approximately 78% compared to that in the pipeline without an arrester. The downstream temperature remains below 50.00 ℃. Under failed flame arrest, the overpressure evolution exhibits three distinct stages. The arrival times of the maximum overpressure peak and the downstream temperature peak are shortened by approximately 45% and 48.57% compared with the no-arrester condition, respectively.

Experimental study on explosion and pressure relief materials in main transformer room of 110 kV underground substation

Yu Sen, Zhang Changshuai

2026, 36(9):  225-230.  doi:10.16265/j.cnki.issn1003-3033.2026.09.2110

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To address the poor applicability of existing pressure relief models to main transformer rooms in 110 kV underground substations, this study employed FLACS numerical simulation to calculate the maximum explosion relief pressure for different relief areas, and proposed an improved explosion pressure calculation formula based on the NFPA 68 model, specifically adapted for high-blockage transformer rooms. Furthermore, explosion relief experiments were conducted to test the rupture characteristics of three types of pressure relief materials: gypsum board, aluminum-magnesium-manganese alloy plate, and aerated concrete. The results indicate that the explosion relief pressure exhibits a nonlinear decrease with increasing relief area; when the relief area increases from 0 to 9 m², the relief efficiency reaches 67.41%, while further enlargement of the relief area yields significantly diminished efficiency gains. To control the maximum explosion relief pressure below 10 kPa, a minimum relief area of 3.13 m² is required, and a relief area of 5-10 m² is recommended to ensure the structural integrity of the building. Among the three partition wall materials, the 12 mm thick gypsum board exhibits the lowest rupture pressure (approximately 2.6 kPa), demonstrating the optimal pressure relief performance.

Public Safety and Emergency Management

Construction and application of a large language model for urban fire rescue command and operations

Wang Xiaolu, Wang Fei, Guo Wei, Shang Xingwei, Jin Ying

2026, 36(9):  231-239.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0342

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To address the problems of delayed information perception, difficulty in multi-source data fusion, high streaming processing latency and low multi-task collaboration efficiency caused by reliance on manual experience and static rules in urban fire rescue command, an LLM-based system for urban fire rescue command and operations was constructed. Based on the Jiu'an emergency management LLM, a domain-specific LLM was developed by integrating high-quality fire industry corpora and adopting strategies of incremental pre-training, supervised fine-tuning and knowledge distillation. A progressive incremental analysis algorithm was designed based on SSM, and a multi-agent collaborative architecture with Model Context Protocol (MCP) and blackboard sharing mechanism was built to support autonomous heterogeneous toolchain invocation driven by global states. The results showed that the system achieved 96.5% accuracy in alarm intention understanding, with average alarm reception and dispatch time reduced from 45 s to 35 s. The first-token latency decreased to 310 ms, and peak memory for long-sequence processing dropped from 82 GB to 24 GB. The blackboard mechanism reduced plan formulation interaction scale by about 45%, and the latency of fire situation judgment and risk warning was compressed to millisecond level. This training system can inject vertical domain knowledge and compress model parameter scale. It supports real-time assessment of incident-related documents and multi-modal streaming data as well as dynamic risk warning, meeting the requirements for response within seconds in fireground operations. The distributed multi-agent architecture enables decentralized business collaboration and significantly reduces system latency and token consumption.

Early warning of electrical fires in high-rise buildings based on improved autoencoder with fusion prediction

Li Chuangchuang, Zhao Jiayi, Wang Baigen, Cheng Kun, Li Bin, Su Sheng

2026, 36(9):  240-247.  doi:10.16265/j.cnki.issn1003-3033.2026.09.1987

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To address the insufficient accuracy of abnormal-state identification in high-rise buildings distribution boxes, an improved autoencoder model with fusion prediction is proposed. First, the data were normalized using the min-max method to eliminate dimensional differences. Second, the model employed a BiGRU to capture temporal dependencies in both forward and backward directions. A scaled dot-product attention (SDA) mechanism was applied to the hidden states of BiGRU to enhance key time-step information Convolutional layers and a channel attention mechanism were also incorporated to extract local correlations among features. Then, a symmetric encoder-decoder structure was adopted, and hidden states from both encoding and decoding phases were concatenated to form a "reconstruction-prediction" dual-task framework, enabling the prediction of electrical parameters for the next time step. Finally, a scoring function based on prediction error was used to quantify sequence anomalies. The results show that root mean square error(RMSE),mean absolute error(MAE), and coefficient of determination R² are 0.000 9, 0.017 8, and 0.731 3, respectively. Compared with XGBoost, gated recurrent unit(GRU), and Transformer, the model shows improved performance in MAE and R² and produces corresponding anomaly-score responses to gradual residual-current drift, abnormal temperature rise, and sudden current disturbances.

Surface fire blocking effect under different pine needle bulk densities and water coverage levels

Kong Weiguang, Pan Yu, Zhang Jinlian, Guo Weihua, Zhao Jinlong

2026, 36(9):  248-255.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0419

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To evaluate the barrier effectiveness of firebreaks in forest firefighting, dead fallen needles of Pinus massoniana were used as fuel, and an experimental platform for surface fire spread was constructed. Six water coverage levels and three fuel bulk densities were set to investigate the barrier effect of firebreaks on fire spread. The results show that, based on the flame spread process and internal temperature distribution, the barrier effects of water-covered firebreaks can be categorized as successful or failed. The success of blocking is closely related to the smoldering propagation process at the bottom of the fuel bed. The actual barrier effectiveness is significantly influenced by the water coverage level and fuel bed bulk density. Successful blocking is achieved when the water coverage level is sufficient to maintain cooling and wetting within the firebreak and to suppress smoldering propagation at the bottom of the fuel bed and subsequent reignition. As the water coverage level increases, a higher moisture content is maintained within the firebreak, smoldering propagation is more effectively suppressed, and the blocking effectiveness is improved. For bulk densities of 33.33, 42.85, and 100 kg/m³, the corresponding critical water coverage levels required for successful blocking are 3.0, 2.0, and 1.0 L/m², respectively. The barrier effect is also improved by a higher fuel bed bulk density, mainly because a higher bulk density leads to lower porosity and poorer oxygen supply conditions. Meanwhile, the bulk density of the fuel bed modifies the flame length and tilt angle during fire spread, ultimately affecting the radiation intensity behind the firebreak.

Occupational Health

Analysis of firefighters' physical fatigue based on fusion of multimodal physiological indicators

Guan Haosen, Zheng Xin, Wang Huan

2026, 36(9):  256-262.  doi:10.16265/j.cnki.issn1003-3033.2026.09.0265

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To accurately identify physical fatigue in firefighters, lower training injury risks, boost emergency rescue efficiency, 18 firefighters were selected as research subjects. Physical fatigue was induced via routine training. The effectiveness of fatigue induction was verified with subjective questionnaire scores and the mean relative error of time perception. Four types of physiological signals, including heart rate variability(HRV), eye movement, electrodermal activity(EDA) and electromyography (EMG), were synchronously collected before and after fatigue. Fourteen significantly different indicators were screened via power analysis, t-test, rank-sum test and Benjamini-Hochberg (BH) correction. Core features were optimized and selected using the minimum Redundancy Maximum Relevance (mRMR) algorithm. Single-modal, dual-modal, trimodal and four-modal fatigue recognition models were built under the multimodal fusion strategy. Recognition verification was implemented by five algorithms: Logistic Regression (LR), K-Nearest Neighbor (KNN), Support Vector Machine (SVM), Adaptive Boosting (AB) and Random Forest (RF). Result shows that heart rate variability (HRV) serves as the optimal single-modal recognition indicator. Multimodal fusion delivers obviously better recognition performance than the single-modal approach. The trimodal combination of EMG + HRV + eye movement acts as the optimal fusion scheme. The Logistic Regression model achieves a recognition accuracy of 91.4% and an average accuracy of 88.7%. It can judge firefighters' physical fatigue states efficiently and accurately.

Intelligent Safety Technology

Fire detection model in confined space based on improved SBR-YOLOv11n

Li Cong, Xu Wenbo, Teng Wenfei, Wang Chenhui, Wu Jiansong

2026, 36(9):  263-270.  doi:10.16265/j.cnki.issn1003-3033.2026.09.1007

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Aiming at the problems of low flame brightness, small target and easy interference in confined space fires, an improved confined space fire detection model SBR-YOLOv11n was proposed based on YOLOv11n model. In the backbone network part, some standard convolution layers were replaced by Space to Depth Convolution (SPDConv) layers to solve the problem that the flame features were easy to lose under low brightness. In the neck network part, the Bidirectional Feature Pyramid Network (BiFPN) module was introduced to improve the fusion effect of small target flame features through bidirectional connections and learnable weight mechanisms. In addition, the Inverted Residual Mobile Block (iRMB) was used to adaptively weight the dynamic flame features to improve the robustness of the model to dynamic flame detection. Experimental results show that the SBR-YOLOv11n model has the best evaluation indexes. Compared with the YOLOv11n model, Precision (P), Recall (R), mean Average Precision (mAP@0.5) and mAP@0.5:0.95 are increase by 5.27 %, 3.81 %, 4.17 % and 3.03 % respectively, reaching 84.94 %, 83.83 %, 84.63 % and 62.97 %, with a detection speed of 75 Frames Per Second (FPS). The SBR-YOLOv11n model meets the needs of rapid and accurate fire detection in confined space and is suitable for fire detection in confined spaces.